Rogue M180 replacement tubes

So last night as I powered off my amps, a terrible squeal came out of thr left speaker. I haven't had a power tube go in some time but my recollection is that the horrible noise I heard is an early sign of tube failure. Seems like I'm going to be in the market for some new tubes! Wondering what other power tubes people have tried in thr M180s and what your experience has been. 

To tell you a little more about my system my pre is a Rogue RP-7 and my s l eaters are Vandersteen Quatro Woods.  While the speakers aren't super efficient, they also have a powered sub so the amps don't have to work that hard as they're not driving the woofers, just tweeter mid and mid bass. Most of what I've read is that the KT120s the amp comes with are most people's favorite because the bass really tightens up but for me, that likely won't change much. Wonferinf if people have different 120s they like other than the stock tung sols or if there are 88s or 90s that people are partial to.